Electrical sound reproduction of gramophone and like records



R. J. MILLER Oct. 11, 1932.

ELECTRICAL SOUND REPRODUCTION OF GRAMOPHONE AND LIKE RECORDS Filed Jan. 23, 1928 fizz/ea er R zmaJmwmzzy Patented Oct. 11, 1932 t UN T ED- STATES REGINALD JAMES MILLEROF LONDON, EN LAND, ASSIGNOR, BY MEsNE AssxeNivmNrs, p TO WESTERN ELECTRIC oo vrrANx NconrortA'rEn, A coaron-A'rroN or NEW YORK V ELECTRICAL SOUND REP nonUcrIo or eRAMor oN 4N1) :LIKE Become Application filed January 23; 1928, Serial No. 248,953, andin G reat Britain January 24, 1927.

This invention relates to the sound reproduction of gramophone and like records wherein electricalv orelectro-magnetic means associated with a source of potential are actuated directly by. a stylus 'which is in contact with the record, andithe invention has for its object to secure more faithful and better controlled reproduction of the recorded sounds than are obtained hitherto. 1

According to one embodiment the invention comprises an electrical sound reproducer provided with a variable inductive energy translator having a m0vable;element which carries a plate of a condenser, means being provided for transmitting mechanical. vibrations to said movable element. 1

According to another aspect the invention comprises an arrangement in which the me.- chanical vibrations of a stylus due to its contact with agramophone or like record are converted into. electrical oscillations through the medium of a condenser coupled mechanically to the moving coil of an electromagnetic reproducer whereby both are actuated simultaneously and directly by said stylus as it vibrates. V p

The condenser'may comprise onevor more stationary insulated conducting plates in proximity to whichmay. be disposed one or more movable insulated conducting plates to rier (not shown) whlch enables the stylus-to 1 which a stylus adapted to contact witha gramophone or other recordimparts move-v ment; said movable plate or platesbeingconnected positively to themoving coil of a known formof electromagnetic reproducer. The invention will be more clearlyunderv "stood byreference .to the appended drawing in which Fig. 1 is an inverted plan view of the reproducer according to the invention. Fig. 2 is a frontelevation of the partsshown inFig. 1; Fig; 3. is arear elevation thereof partly in section; Fig. 4c is a side elevation thereof and Fig. 5 is a circuit arrangement in which the reproducer may be conveniently arranged to perform its desiredfunctions.

The holder 1, forming part of the energy translator, is lPlVOtGCl-lfla bracket 2 carried 7 by a block 8 which issecured to a permanent magnet The holder is preferably of extremely light material so that its inertia is magnet and secured to the block 3Jis a soft iron core 9, about which is supportedthe moving coil 6. A set screw 10 may be .used

in the ordinary wayadjustably-to secure the stylus-in position. An insulated plate,12 extending preferably over the whole of one side of the member 1 is attached theretoand con I stitutes oneelectrode of a condenser. The

other electrode'consists of an insulated plate 13 which is fixed to the pole piece 11 in the manner shown. Connecting leads l jointhe condenser plates 12 and 13 to terminals 15.

Adjustment of the movable part with respect tothe fiXed parts may be effected. by means of set screws 16. Springs 17 tendjtoretainv the holder in a normal position against the eifectsofthe received vibrations. I

The-device issupported ina suitable car-J engage with a gramophone record or the like so that lateral vibrations may be imparted .to. the movablevholder 1. 'These vibrations cause varying currents to be inducedin the coil 6 20 and resistance21'are connectedas shown so that for varying potentials received at b6 177.

minals 19 the tube may serve. as an amplifier to produce amplifiedcurrent in the trans,-.

former 22. v

Space discharge currentis derived high tension battery (notlshown) connected 85 and simultaneously vary thevcapacity of the between 28 and E. The low tension filament heating current is supplied from the battery (not shown) at terminals 27. In order that the condenser 12, 13 of the reproducer may be effective its plates have impressed thereon a steady potential conveniently obtained as shown by coupling one of terminals 19 through resistances 31, 30 to the high tension battery at terminal 28, the other plate (12) ofthe condenser being earthed. The

condenser 32 and resistance 31 are provided merely to prevent any line or battery noises from reaching the grid of tube 18..

To the output winding of transformer 22 the moving coil 6 is connected through terminals 23. ,An appropriate receiving instru ment is. connected .to terminals26 or when the apparatus is used in a public address system, a further amplifier would be coupled to terminals 26, the loud speaker unit being then connected to the output of this amplifier.

I Shunt'resistances 24 and 25 are supplied incthe output circuit of transformer 22 and these have variable tappin'gs by means of a which the relative magnitudes of the currents received from the moving coil 6 and from the 7 tube 18 ma'y be regulated to give most satis factory reproduction in the recelving' circuit coup'led'to terminals 26.

The operation of the reproducer circuit will be clearly understood from the drawing. The condenser 12,13 with its associated circuits is sensitive to low frequency signals but for the high frequenciesis not so responsive.

High frequencies however are faithfully ree produced by the moving coil element whose efiiclency as a reproducer falls oil at the lower frequeneles The entire range of frequencies is therefore impressed on the circuit oftube 18 and by this means with the help o'f regu lator resistances 24 and'25 the vibrations of the reproducer may be convertedjinto electrical waves whose characteristics 7 faithfully represent the impressionsof the record. Furthermore by suitable regulationthe reproducer may be made to compensate-at the 'lower'frequencies for the known deficiencies inherent in existing loud speakers.

V The above description has been restricted to the particular device and circuit illus- 'trated, but many modifications and alterations may be made without departing from the principle of the invention. For example, it is conceivable that the-above arrangenients may be used in conjunction with, or in-part be substituted by, a resistance, varied in accordance with mechanical vibrations.

. The induced current may be set up in a sta tionary coil witha vibratable'core instead of using the moving coilas above described.

While the invention'has been described.

with reference to specific embodiments it is to be understood that the scope of-the'invenasdefined in the appended claims.

transmitting mechanical vibrations to said translator.

8. In an electrical phonograph-reproducer, aJmagnet structure, a variable inductive energy translator situated in the field thereof, a coil on said translator, a condensercomprising a plate carriedby said'translator and a plate carried; by said structure, a stylus for transferring mechanical vibrations to said translator, and connecting conductors for transferring the translated mechanical vibrations to an electrical circuit.

4. In-an electrical'phonogra'ph reproducer, a permanentmagnet, a moving coil in the field of said magnet, a movable membersupporting said coil, a condenser comprisingv a plate supportedby said movable member and Ii a stationary plate secured to said magnet, a stylus support, and a stylus for transferring mechanical vibrations from a record to said movable member. I V

5. In an electrical phonograph reproducer, a magnet'structure, a Variable inductive en erg-y translator situated in the field thereof, a coil on said translator, a condenser comprising a plate carried by said translator and a plate carried by said structure, a stylus for transferring mechanical vibrations to'said translator, and conductors connecting said condenser tothe input circuit of a vacuum tube amplifier and other conductors connecting said inductive energy translator to an output circuit of said vacuum tube.

' 6.- A system for reproducing sound including a vibration translating device and a vacuum tube amplifier, the device comprising a vibrating body, a variable condenser adapted.

condenser coupled to the circuit and adapted tobe varied by the body, and a coil independently'c oupled to the circuit and'bei'ng 1 inductively related to the body 8. In a vibration f translating device," a'

vibrating body, a vacuum tube amplifier,two

circuits connecting the amplifierand the body, m ans associated with the body and 1 301 L prising a variable inductive energy translator,

one of the circuits for generating variations lnductively, and other means associated wlth the body and the other circuit for generating variations capacitatively. V I

9. An electric phonograph reproducer coma variable capacitative energy translator, a vibratable actuating member common to the translators, and a stylus for transferringv mechanical vibrations to the member.

10. An electrical phonograph reproducer comprising two energy translators for translating mechanical vibrationsinto electrical variations, one translator being more sensitive to the lower frequencies Whilst the other 7 is more sensitive to the higher frequencies of plate supported in spaced relation thereto by the said vibratory element, and an electromagnetic unit comprising a coil and an armature supported by said vibratory element in the field of the coil.

12. In a device of the class described, a vibratory element, means carried thereby for supporting a phonographic stylus, a capacity unit comprising a condenser plate fixedly supported in juxtaposition to said vibratory element and a companion condenser plate supported in spaced relation thereto by said vibratory element, and an electromagnetic unit comprising a fixed magnet, a coil arranged between the pole pieces of the magnet, and an armature supported by said vibratory element in the field of the coil and between the pole pieces of themagnet.

REGINALD JAMES MILLER. 

